Radiation analyzing apparatus

ABSTRACT

A wave height analyzer generates pre-sensitivity correction data using a radiation pulse signal transmitted from a room temperature amplifier, a heater value acquired from a temperature control section, a base line of a current flowing to a TES acquired from a base line monitor mechanism. The wave height analyzer outputs the pre-sensitivity correction data to a sensitivity correction arithmetic operation unit and receives post-sensitivity correction data, on which sensitivity correction is performed. The wave height analyzer generates composite data of a combination of the pre-sensitivity correction data and the post-sensitivity correction data. A spectrum display section receives pieces of composite data sequentially created by the wave height analyzer and displays at least one of a spectrum before sensitivity correction and a spectrum after sensitivity correction, in response to receiving an operator&#39;s request.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Japanese Patent Application No.2015-008548 filed on Jan. 20, 2015, the entire subject-matter of whichis incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to a radiation analyzing apparatus including aradiation detector constituted by a superconductive transition edgesensor.

BACKGROUND

Examples of a radiation analyzing apparatus capable of discriminatingradiation energy include an energy dispersive spectroscopy (hereinafter,referred to as EDS) and a wavelength dispersive spectroscopy(hereinafter, referred to as WDS).

The EDS is an X-ray detector of a type that converts the energy ofX-rays taken into a detector into an electrical signal in the detectorand calculates the energy by the magnitude of the electrical signal. Inaddition, the WDS is an X-ray detector of a type that monochromatizes(energy discrimination) X-rays using a spectroscope and detects themonochromatized X-rays using a proportional counter tube or the like.

As the EDS, semiconductor detectors such as a silicon lithium (SiLi)type detector, a silicon-drift type detector, and a germanium detectorare known. For example, a silicon lithium type or silicon-drift typedetector is often used in an element analyzing apparatus of an electronmicroscope, and can detect energy in a wide range from approximately 0.2keV to 20 keV. However, since silicon is used for the detector, theproperties thereof, in principle, depend on a band gap (approximately1.1 eV) of silicon, and thus it is difficult to improve an energyresolution to equal to or greater than approximately 130 eV, and theenergy resolution becomes lower by 10 times or more than that of theWDS.

In this manner, the wording “energy resolution which is one of indexesindicating the performance of an X-ray detector is, for example, 130 eV”means that energy can be detected by uncertainty of approximately 130 eVwhen the X-ray detector is irradiated with X-rays. Therefore, as theuncertainty becomes lower, the energy resolution becomes higher. Thatis, when characteristic X-rays constituted by two adjacent spectrums aredetected, uncertainty becomes lower as an energy resolution becomeshigher. When a difference in energy between two adjacent peaks isapproximately 20 eV, it is possible to, in principle, separate the twopeaks from each other by an energy resolution of approximately 20 eV to30 eV.

In recent years, superconductive X-ray detectors, which are energydispersive type detectors, having the same energy resolution as that ofa WDS have attracted attention. Among these superconductive X-raydetectors, a detector including a superconductive transition edge sensor(hereinafter, referred to as a TES) is a high-sensitivity calorimeterusing a sharp resistance change (for example, a resistance change is0.1Ω when a temperature change is several mK) when a metal thin filmtransitions from a superconductive state to a normal conductive state.Incidentally, the TES is also referred to as a micro calorie meter.

The TES analyzes a sample by detecting a temperature change occurringwithin the TES when fluorescent X-rays or characteristic X-raysgenerated from the sample by radiation irradiation with primary X-rays,primary electron beams, or the like are incident thereon. The TES has anenergy resolution higher than those of other detectors, and can obtainan energy resolution of, for example, equal to or less than 10 eV incharacteristic X-rays of 5.9 keV.

When a TES is installed in a scanning electron microscope or atransmission electron microscope, characteristic X-rays generated from asample irradiated with an electron beam are acquired by the TES, andthus it is possible to easily separate peaks of energy spectrums ofcharacteristic X-rays (for example, Si-Kα, W-Mα, or W-Mβ) which are notseparable by a semiconductor type X-ray detector.

Incidentally, in an X-ray analyzing apparatus adopting thesuperconductive X-ray detector, a superconducting quantum interferencedevice (hereinafter, referred to as a SQUID) amplifier is used to readout an extremely small current change in the TES. In order to realize ahigh energy resolution of the TES, it is important to keep a currentflowing to the SQUID amplifier constant. This is because a change in acurrent flowing to the SQUID amplifier has to be reduced in order toobtain a high energy resolution, as described later.

As an apparatus for keeping a current flowing to the SQUID amplifier,that is, a base line current flowing to the TES constant, there isknown, for example, an X-ray analyzing apparatus that corrects, when thebase line current flowing to the TES deviates from a fixed value andfluctuates, a current flowing to the TES or a wave height value basedon, the current in accordance with the fluctuation width thereof (see JP2009-271016 A).

In addition, there is known a radiation analyzing apparatus thatcorrects a wave height value of a signal pulse of a TES on the basis ofcorrelation between an output of a heater embedded into a pedestalhaving the TES installed thereon and a base line current flowing to theTES (see JP 2014-38074 A). The radiation analyzing apparatus acquires inadvance characteristics of the correlation between the output of theheater and the sensitivity of the TES, and corrects the wave heightvalue of the signal pulse of the TES using the sensitivity of the TEScorresponding to the output of the heater when a signal pulse of the TESis acquired during the actual measurement.

However, in the above-mentioned X-ray analyzing apparatus and radiationanalyzing apparatus, a signal pulse is only corrected on-line oroff-line using a base line current and each of outputs of a heater. Itis desired that versatility, expandability, compatibility, and the likefor associating signal processing including the correction of a signalpulse with various processing modes are secured.

SUMMARY

Illustrative aspects of the present invention provide a radiationanalyzing apparatus capable of easily associating signal processingincluding the correction of a signal pulse with various processingmodes.

(1) According to one illustrative aspect of the present invention, theremay be provided a radiation analyzing apparatus comprising: asuperconductive transition edge sensor configured to detect radiation; adata acquisition unit configured to acquire a physical quantity of datahaving correlation with sensitivity of the superconductive transitionedge sensor; a sensitivity correction unit configured to correct adetection signal, which is output from the superconductive transitionedge sensor in accordance with the sensitivity of the superconductivetransition edge sensor, by using information regarding the correlationbetween the physical quantity of data acquired by the data acquisitionunit and the sensitivity of the superconductive transition edge sensor;and a spectrum generation unit configured to generate an energy spectrumof the radiation with respect to each of a detection signal, which isoutput from the superconductive transition edge sensor, and a signalobtained by performing sensitivity correction on the detection signal bythe sensitivity correction unit.

According to the radiation analyzing apparatus of the aspect describedin the above (1), the spectrum generation unit generating an energyspectrum corresponding to the presence or absence of sensitivitycorrection performed by the sensitivity correction unit is provided, andthus it is possible to perform various processes corresponding to eachof the presence and absence of sensitivity correction, and various typesof processes such as comparison between the presence and absence ofsensitivity correction, in each of an on-line mode during radiationdetection and an off-line after the termination of radiation detection.

(2) In the radiation analyzing apparatus according to the above (1),wherein the spectrum generation unit is configured to output signal datathat is obtained by adding the physical quantity of data to thedetection signal output from the superconductive transition edge sensor,and wherein the sensitivity correction unit is configured to, by usingthe signal data output from the spectrum generation unit, whilegenerating the information regarding correlation between the physicalquantity of data and the sensitivity of the superconductive transitionedge sensor, correct the detection signal by using the informationregarding correlation.

Further, in the case of the above (2), there is provided the sensitivitycorrection unit correcting a detection signal while generatinginformation regarding correlation whenever pieces of signal dataincluding a detection signal are sequentially received in an on-linemode and an off-line mode, and thus it is possible to improve thecorrection accuracy of the detection signal while improving the accuracyof the information regarding correlation in association with the storageof the detection signal.

(3) In the radiation analyzing apparatus according to the above (2),wherein the sensitivity correction unit is configured to, by using thesignal data obtained over the period of time, repeatedly update theinformation regarding correlation for each period of time until apredetermined condition is satisfied.

Further, in the case of the above (3), the information regardingcorrelation is generated using pieces of signal data obtained over aperiod of time until a predetermined condition is satisfied with respectto a statistic or a detection time of a detection signal, and thus it ispossible to improve the accuracy of the information regardingcorrelation. Further, the information regarding correlation isrepeatedly updated, and thus it is possible to improve the correctionaccuracy of the detection signal while improving the accuracy of theinformation regarding correlation in association with the storage of thepieces of signal data.

(4) In the radiation analyzing apparatus according to any one of theabove (1) to (3), wherein the data acquisition unit acquires an outputof a heater, which is configured to heat the superconductive transitionedge sensor, as the physical quantity.

Further, in the case of the above (4), it is possible to appropriatelycorrect the detection sensitivity of the superconductive transition edgesensor with respect to an output of the heater having correlation withthe detection sensitivity of the superconductive transition edge sensor.

(5) In the radiation analyzing apparatus according to any one of theabove (1) to (3), wherein the data acquisition unit acquires a currentflowing to the superconductive transition edge sensor as the physicalquantity.

Further, in the case of the above (5), it is possible to appropriatelycorrect the detection sensitivity of the superconductive transition edgesensor with respect to a current flowing to the superconductivetransition edge sensor having correlation with the detection sensitivityof the superconductive transition edge sensor.

(6) In the radiation analyzing apparatus according to any one of theabove (1) to (5), further comprising: a display configured to display anenergy spectrum of the radiation corresponding to each of presence andabsence of sensitivity correction performed by the sensitivitycorrection unit.

Further, in the case of the above (6), it is possible to performpresentation so that an operator can easily visually compare energyspectrums according to the presence and absence of sensitivitycorrection with each other in each of an on-line mode during radiationdetection and an off-line mode after the termination of radiationdetection.

(7) In the radiation analyzing apparatus according to the above (6),wherein the display is configured to display the information regardingthe correlation.

Further, in the case of the above (7), it is possible to performpresentation so that an operator can easily visually ascertain theaccuracy of sensitivity correction in each of an on-line mode duringradiation detection and an off-line mode after the termination ofradiation detection.

(8) In the radiation analyzing apparatus according to the above (6) or(7), wherein the display is configured to display a setting screen forsetting conditions for generating the information regarding correlationby the sensitivity correction unit, in response to receiving anoperator's input.

Further, in the case of the above (8), it is possible to performpresentation so that an operator can easily control the state ofsensitivity correction performed by the sensitivity correction unit, ineach of an on-line mode during radiation detection and an off-line modeafter the termination of radiation detection.

According to the radiation analyzing apparatus of the present invention,the spectrum generation unit generating an energy spectrum correspondingto the presence or absence of sensitivity correction performed by thesensitivity correction unit is provided, and thus it is possible toeasily associate various processes corresponding to each of the presenceand absence of sensitivity correction and signal processing includingcomparison between the presence and absence of sensitivity correctionwith various types of processes, in each of an on-line mode duringradiation detection and an off-line mode after the termination ofradiation detection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a configuration of aradiation analyzing apparatus according to an embodiment of the presentinvention;

FIG. 2 is a schematic diagram illustrating a configuration of a portionof the radiation analyzing apparatus according to the embodiment of thepresent invention;

FIG. 3 is a schematic diagram illustrating a configuration of a portionof the radiation analyzing apparatus according to the embodiment of thepresent invention;

FIG. 4 is a schematic diagram illustrating a configuration of a TES ofthe radiation analyzing apparatus according to the embodiment of thepresent invention;

FIG. 5 is a diagram illustrating an example of a setting screendisplayed by a spectrum display section of the radiation analyzingapparatus according to the embodiment of the present invention;

FIG. 6 is a diagram illustrating an example of data exchange in a waveheight analyzer, a sensitivity correction arithmetic operation unit, andthe spectrum display section of the radiation analyzing apparatusaccording to the embodiment of the present invention;

FIG. 7 is a diagram illustrating an example of a spectrum formed by dataused when the sensitivity correction arithmetic operation unit of theradiation analyzing apparatus according to the embodiment of the presentinvention sets a first sensitivity correction value and a secondsensitivity correction value;

FIG. 8 is a diagram illustrating an example of data of a combination ofthe first sensitivity correction value generated by the sensitivitycorrection arithmetic operation unit of the radiation analyzingapparatus according to the embodiment of the present invention and anaverage value of heater values; and

FIG. 9 is a diagram illustrating an example of data of a combination ofthe second sensitivity correction value generated by the sensitivitycorrection arithmetic operation unit of the radiation analyzingapparatus according to the embodiment of the present invention and anaverage value of base lines.

DETAILED DESCRIPTION

Hereinafter, a radiation analyzing apparatus according to anillustrative embodiment of the present invention will be described withreference to the accompanying drawings.

A radiation analyzing apparatus 100 according to the presentillustrative embodiment is an apparatus which is usable as a compositionanalyzing apparatus such as an electron microscope, an ion microscope,an X-ray microscope, or a fluorescent X-ray analyzing apparatus.

As illustrated in FIG. 1, the radiation analyzing apparatus 100 includesa TES 1, a sensor circuit section 2, a bias current source 3, a currentdetection mechanism 4, a wave height analyzer 5, a first thermometer 6,a sensitivity correction arithmetic operation unit 7, and a spectrumdisplay section 8.

The TES 1 detects radiation energy as a temperature change whenreceiving radiation, and outputs the temperature change as a currentsignal. The sensor circuit section 2 is connected to the TES 1. The biascurrent source 3 applies a current for making the sensor circuit section2 perform constant voltage driving in a pseudo manner, to the sensorcircuit section 2. The current detection mechanism 4 detects a currentflowing to the TES 1. The wave height analyzer 5 measures a wave heightvalue of a signal pulse detected by the current detection mechanism 4.The first thermometer 6 is embedded into a pedestal for installing thesensor circuit section 2 and measures the temperature of a heat sinkhaving the TES 1 installed thereon. The sensitivity correctionarithmetic operation unit 7 corrects a wave height value of a signalpulse measured by the wave height analyzer 5 on the basis of temperaturedata output from the first thermometer 6 and a fluctuation in currentflowing to the TES 1. The spectrum display section 8 displays an energyspectrum using a signal pulse having been subjected to sensitivitycorrection by the sensitivity correction arithmetic operation unit 7.

Hereinafter, the principle of operation of the TES 1 according to theillustrative embodiment of the present invention will be described. TheTES 1 uses superconductive transition of a superconductive body, andholds an operation point in an intermediate state between a normalconductive state and a superconductive state in a detection operation ofradiation. Thereby, when one piece of radiation is absorbed into the TES1, for example, a resistance change of several mΩ is obtained withrespect to a temperature fluctuation of 100 μK in a state where theoperation point is held during superconductive transition, and thus itis possible to obtain a radiation pulse of the μA order.

In addition, data obtained by measuring in advance a relationshipbetween a pulse wave height value and radiation energy is stored, andthus it is possible to detect the energy of incident radiation from asignal pulse wave height value even when the TES 1 is irradiated withradiation having unknown energy.

In order to hold the TES 1 in the operation point during thesuperconductive transition, the operation point of the TES 1 isdetermined by a heat balance between a current (hereinafter, referred toas a TES current It) which flows to the TES 1 and a heat link to a heatsink provided within the TES 1. Since the energy resolution of the TES 1is a function of temperature, the temperature may be lowered as much aspossible. The heat sink temperature is set to, for example,approximately 50 mK to approximately 400 mK. The TES current It isdetermined by the following Expression 1.It ² Rt(T)=G(T−Tb)  (1)

In Expression 1 mentioned above, the TES current It is described by anoperation resistance Rt of the TES 1, a thermal conductivity G of theheat link for thermally connecting a second thermometer 17 (describedbelow with reference to FIG. 4) provided in the TES 1 and the heat sink,a temperature T of the second thermometer 17, and a temperature Tb ofthe heat sink.

Further, a relationship between the TES current It and a pulse waveheight value ΔI is given by the following Expression 2. Ideally, whenthe TES current It is constant, always a constant pulse wave heightvalue ΔI is obtained.

$\begin{matrix}{{It} = {\frac{CT}{\alpha\; E}\Delta\; I}} & (2)\end{matrix}$

In Expression 2 mentioned above, the TES current It and the pulse waveheight value ΔI are described by a sensitivity α of the TES 1, a heatcapacity C, an energy E of emitted radiation, and a temperature T of thesecond thermometer 17. As seen from Expression 2, when a base linecurrent flowing to the TES 1 varies, a wave height value of a signalpulse varies even when the TES 1 is irradiated with pieces of radiationhaving the same energy. In addition, as seen from Expression 1, when thetemperature of the heat sink varies, the base line current flowing tothe TES 1 varies. That is, when the heat sink fluctuates, the pulse waveheight value ΔI also fluctuates, which results in a deterioration inenergy resolution.

In response to the TES 1 being irradiated with radiation, a wave heightvalue of a signal pulse associated with a temperature change occurringwithin the TES 1 changes to an increasing trend in association with anincrease in a current (same as the TES current It) which flows to theSQUID amplifier 11, in accordance with Expression 2 mentioned above. Asan example of the pulse wave height value ΔI, a calculation valueobtained by processing a pulse signal using a band filter and thenconvoluting the processed signal is output to the spectrum displaysection 8.

At this time, a spectrum display screen in the spectrum display section8 is displayed by representing a horizontal axis as a pulse wave heightvalue ΔI and representing a vertical axis as a count. For example, whenthe pulse wave height value ΔI is 100, one is counted at the location of100. A radiation spectrum is formed by repeating this process.

This means that a change in an output value after filtering in spite ofthe same energy results in a variation in the pulse wave height valueΔI. The degree of variation is equivalent to the above-mentioned energyresolution. That is, in order to realize a high energy resolution, avariation in the pulse wave height value ΔI has to be reduced withrespect to the same energy.

The variation in the pulse wave height value ΔI is caused by a change ina current flowing to the SQUID amplifier 11. Therefore, as describedabove, in order to realize a high energy resolution, it is important tomake a current flowing to the SQUID amplifier 11 constant or to adoptmeans for making the pulse wave height value ΔI constant even when acurrent flowing to the SQUID amplifier 11 changes.

Hereinafter, the radiation analyzing apparatus 100 according to theillustrative embodiment of the present invention will be described indetail.

The sensor circuit section 2 includes a shunt resistor 9 that has aresistance value smaller than that of the TES 1 and is connected to theTES 1 in parallel, and an input coil 10 which is connected to the TES 1in series.

In the sensor circuit section 2, when a bias current is applied from thebias current source 3, the current is branched at a resistance ratio ofa resistance value of the shunt resistor 9 to a resistance value of theTES 1. That is, a voltage value of the TES 1 is determined by a currentflowing to the shunt resistor 9 and a voltage determined by a resistancevalue of the shunt resistor 9.

The current detection mechanism 4 includes the SQUID amplifier 11, and aroom temperature amplifier 15 for amplifying and shaping an electricalsignal which is output from the SQUID amplifier 11. Incidentally, as thecurrent detection mechanism 4, the SQUID amplifier 11 and the roomtemperature amplifier 15 which use the input coil 10 are used, but otherconfigurations can be adopted insofar as a change in a current flowingto the TES 1 can be detected.

As illustrated in FIG. 2, the TES 1, the shunt resistor 9, and the SQUIDamplifier 11 are provided at the tip of a cold head 12 which is cooledup to 50 mK to 400 mK by a refrigerator. Incidentally, the TES 1 and theSQUID amplifier 11 are connected through a superconductive wiring 13. Asanother example, as illustrated in FIG. 3, the TES 1 may be provided atthe tip of the cold head 12, and the SQUID amplifier 11 may be providedat the tip of a cold block 14 which is cooled up to 9 K or less.Incidentally, the shunt resistor 9 is not shown in FIGS. 2 and 3.

The wave height analyzer 5 is a multi-channel pulse height analyzer thatobtains a wave height value (voltage value) of a signal pulse from aradiation pulse signal transmitted from the room temperature amplifier15 to thereby generate an energy spectrum. The wave height analyzer 5reads a wave height value of a radiation pulse, and adds one count tothe location of the wave height value in a graph in which a verticalaxis represents a count and a horizontal axis represents a wave heightvalue. The wave height analyzer 5 has a function of repeating the sameoperation on signal pulses of a plurality of pieces of radiation tothereby create a histogram and displaying the created histogram on thespectrum display section 8. The wave height analyzer 5 is one example ofa spectrum generation unit. Incidentally, the generation of specificdata will be described later.

In addition, when correction data for converting a voltage value of asignal pulse into energy in advance is incorporated in the wave heightanalyzer 5 or the spectrum display section 8, it is possible to displaya spectrum in which a vertical axis represents a count and a horizontalaxis represents energy.

The first thermometer 6 for monitoring the temperature of the cold head12 is provided inside the cold head 12. The first thermometer 6 can beformed using a semiconductor, a superconductive body, or a metal oxide.For example, the first thermometer 6 can be formed using ruthenium oxideor germanium. The first thermometer 6 is configured to have a resistancevalue changing along with the temperature of the cold head, and canmeasure temperature by associating in advance temperature with anelectrical signal (in general, a voltage signal) which is output fromthe first thermometer 6. It is possible to ascertain a temperature stateof the cold head 12 using temperature when temperature and resistanceare associated with each other in advance and directly using anelectrical signal when temperature and resistance are not associatedwith each other.

The sensitivity correction arithmetic operation unit 7 is a mechanismfor correcting a wave height value of a signal pulse which is outputfrom the room temperature amplifier 15, that is, a detection sensitivityof the TES 1. The sensitivity correction arithmetic operation unit 7receives data and an electrical signal of the power of a heater 20 usedto make the temperature of the first thermometer 6 constant, and asignal of the amount of change in a bias current which is output from abase line monitor mechanism 31 to be described later, and corrects apulse wave height value ΔI of the signal pulse. The sensitivitycorrection arithmetic operation unit 7 includes an arithmetic operationcircuit for performing the above-mentioned correction process, and amemory, and is realized by program processing using a personal computeror the like, or is realized by dedicated hardware. In addition, thesensitivity correction arithmetic operation unit 7 may be integratedinto the wave height analyzer 5 and the spectrum display section 8.Incidentally, a specific sensitivity correction method will be describedlater.

The spectrum display section 8 includes an arithmetic operation circuit,a memory, and a display such as a liquid crystal display. The arithmeticoperation circuit and the memory of the spectrum display section 8 arerealized by, for example, program processing using a personal computeror the like, or are realized by dedicated hardware. The spectrum displaysection 8 displays a setting screen for setting operation conditions ofthe sensitivity correction of the sensitivity correction arithmeticoperation unit 7, and the like in accordance with an operator's inputoperation, and outputs an instruction signal in response to the inputoperation in the setting screen to the sensitivity correction arithmeticoperation unit 7.

The spectrum display section 8 displays an energy spectrum of radiationdetected by the TES 1, data of the first sensitivity correction value k1and the second sensitivity correction value k2 which are set by thesensitivity correction arithmetic operation unit 7 as necessary, and thelike on the display in response to an operator's request or the like,using spectrum data received by the wave height analyzer 5. The spectrumdisplay section 8 displays an energy spectrum generated by a wave heightvalue ΔI of a signal pulse corresponding to each of the presence andabsence of sensitivity correction performed by the sensitivitycorrection arithmetic operation unit 7. The spectrum display section 8displays an energy spectrum used when the sensitivity correctionarithmetic operation unit 7 sets the first sensitivity correction valuek1 and the second sensitivity correction value k2. The spectrum displaysection 8 displays data of the first sensitivity correction value k1 andthe second sensitivity correction value k2 which are set by thesensitivity correction arithmetic operation unit 7 on the display.Incidentally, the display of specific data will be described later.

Hereinafter, the principle of sensitivity correction performed by thesensitivity correction arithmetic operation unit 7 according to theillustrative embodiment of the present invention will be described. Asillustrated in FIG. 4, the TES 1 includes an absorber 16, a secondthermometer 17, and a membrane 18. The absorber 16 is a metal band, asemimetal, a superconductive body, or the like for absorbing radiationsuch as X-rays. The absorber 16 is formed of, for example, gold, copper,or bismuth. The second thermometer 17 is constituted by asuperconductive body, and detects heat generated by the absorber 16 as atemperature change. The second thermometer 17 is formed of, for example,a material including two layers of titanium and gold. The membrane 18thermally loosely connects the second thermometer 17 and the cold head12, and controls a flow rate of heat escaping to a heat sink (cold head12, not shown). The membrane 18 and the heat sink are formed of, forexample, silicon nitride.

In order to hold the resistance value of the TES 1 in an intermediatestate between a normal conductive and a superconductive, Joule heatgenerated by the second thermometer 17 thermally balances with the flowof heat flowing from the second thermometer 17 (or the absorber 16) tothe cold head 12 through the membrane 18.

The thermal balance between Joule heat and the flow of heat travelingthrough the membrane 18 is given by Expression 1 mentioned above. InExpression 1 mentioned above, when it is considered that the TES currentIt is affected by a thermal fluctuation Pex from the outside of the TES1, Expression 1 mentioned above is rewritten as Expression 3.

$\begin{matrix}{{{{It}^{2}{{Rt}(T)}} + {\left( {V + \frac{GT}{I\;\alpha}} \right)\delta\;{It}} + {Pex}} = {G\left( {T - {Tb}} \right)}} & (3)\end{matrix}$

When the thermal fluctuation Pex from the outside of the TES 1increases, δft in a second term on the left side decreases so as tosatisfy Expression 3 mentioned above. Incidentally, examples of thethermal fluctuation Pex from the outside include a temperaturefluctuation of the cold head 12 cooling the TES 1, a fluctuation in heatradiation due to a temperature fluctuation of a heat shield 19surrounding the cold head 12, and a temperature fluctuation of the heatshield 19 due to heat conduction to the TES 1 from the heat shield 19through a remaining gas which is present inside a refrigerator.

Regarding a relationship between a pulse wave height value ΔI and acurrent flowing to the TES 1, the pulse wave height value ΔImonotonously increases as the current flowing to the TES 1 increases asexpressed by Expression 2 mentioned above. That is, in order to make thepulse wave height value ΔI with respect to pieces of radiation havingthe same energy constant, it is important to make the current flowing tothe TES 1 constant.

In addition, the TES 1 is required to be cooled up to approximately 100mK. Examples of a cooling unit include a dilution refrigerator and anadiabatic demagnetization refrigerator (hereinafter, referred to as anADR). The former refrigerator relates to a technique for performingcooling using an enthalpy difference when 3He melts from a conc. phase(strong phase) to a dilute phase (weak phase) within a mixing chamber.The latter refrigerator relates to a technique for applying a magneticfield to a magnetic body to align the direction of spin and cooling anobject connected to the magnetic body by an increase in enthalpy whenremoving the magnetic field. In both the refrigerators, the cold head 12is installed at a location which is most cooled. In the dilutionrefrigerator and the ADR, the first thermometer 6 for measuringtemperature is installed in the cold head 12, and it is possible toobtain temperature information of the cold head 12 by monitoring anelectrical signal (in general, a voltage signal) which is output fromthe first thermometer 6. It is possible to ascertain temperature in realtime by registering in advance a relationship between an electricalsignal and temperature in a temperature control section 21. Thetemperature control section 21 is installed between the firstthermometer 6 and the sensitivity correction arithmetic operation unit7, and has a function of transmitting temperature data obtained by thefirst thermometer 6 or an electrical signal to the sensitivitycorrection arithmetic operation unit 7.

When the temperature of the cold head 12 is kept constant in thedilution refrigerator, the heater 20 is installed. The heater 20 isconnected to the temperature control section 21. When a targettemperature is set in the temperature control section 21, thetemperature control section 21 controls an output of the heater 20 onthe basis of temperature data of the first thermometer 6 or anelectrical signal. In the case of the ADR, the temperature of the coldhead 12 is kept constant by controlling the intensity of a magneticfield applied to a magnetic body on the basis of the temperature data ofthe first thermometer 6 or the electrical signal. Hereinafter, a methodfor correcting sensitivity on the basis of a dilution refrigerator willbe described, but the same method can also be applied to an ADR.

As seen from Expression 1 and Expression 2, when the temperature of aheat sink falls, a pulse wave height value ΔI increases. In contrast,when the temperature of a heat sink rises, a pulse wave height value ΔIdecreases. The temperature of the heat sink is monitored in the firstthermometer 6. The temperature control section 21 adjusts an output ofthe heater 20 so that the temperature of the first thermometer 6 becomesconstant, and adjusts temperature so that the first thermometer 6 has aconstant value. For example, when the temperature of the heat sinkfalls, in order to make the temperature of the first thermometer 6constant, the temperature control section 21 increases the output of theheater 20. The temperature control section 21 acquires an output valueof the heater 20 (hereinafter referred to as a heater value) andtransmits the acquired output value of the heater 20 to the sensitivitycorrection arithmetic operation unit 7. The temperature control section21 is one example of a data acquisition unit.

In a relationship between an output of the heater 20 and a pulse waveheight value ΔI, the pulse wave height value ΔI changes to an increasingtrend in association with an increase in the output of the heater 20.The output of the heater 20 is controlled so that the first thermometer6 always keeps a constant value. As described above, a heater valuechanges due to the invasion of heat from the outside. The sensitivitycorrection arithmetic operation unit 7 defines a pulse wave height valueΔI of a certain heater value as a reference value, and stores arelationship between a result (first sensitivity correction value k1),which is obtained by dividing the pulse wave height value ΔI by thereference value, and the output of the heater 20. The first sensitivitycorrection value k1 changes to a decreasing trend in association with anincrease in the output of the heater 20. When characteristics of thefirst sensitivity correction value k1 and the output of the heater 20are once obtained, it is possible to obtain an accurate pulse waveheight value ΔI by correcting a pulse wave height value ΔI which isactually obtained, using the first sensitivity correction value k1corresponding to the actual output of the heater.

Similarly, when a relationship between a fluctuation in a currentflowing to the TES 1 and a fluctuation in pulse wave height value ΔI isobtained in advance, it is possible to perform correction on a detectedpulse wave height value ΔI. A change in a current flowing to the TES 1is monitored by the base line monitor mechanism 31, and correction isperformed on a pulse wave height value ΔI detected in accordance withthe value, and thus it is possible to avoid a problem in that pulse waveheight values ΔI are different from each other when pieces of radiationhaving the same energy are incident, due to external disturbance.

The base line monitor mechanism 31 monitors a change in a currentflowing to the TES 1, and transmits the amount of change in a biascurrent to the sensitivity correction arithmetic operation unit 7 as asignal. The sensitivity correction arithmetic operation unit 7 correctsan output signal from the room temperature amplifier 15 in accordancewith the amount of change in the bias current. The base line monitormechanism 31 is one example of a data acquisition unit.

An upper limit and a lower limit can be set in the base line monitormechanism 31 with respect to the signal from the room temperatureamplifier 15, and a signal falling within the range is recognized as abase line.

For example, when the upper limit and the lower limit are respectivelyset to +100 mV and −100 mV, a signal from the room temperature amplifier15 which falls within the range is always recognized as a base linesignal. A fluctuation in a base line current is slower than a responsefrequency (equal to or higher than 100 Hz) of the TES 1, and thus it isdesired that a current in the SQUID amplifier 11, that is, a samplingfrequency of a current of the TES 1 is equal to or less than acommercial power frequency of 50 Hz. In addition, since the sampledcurrent of the TES 1 has a statistical fluctuation, it is preferablethat, for example, N pieces of sampling data are averaged and theaveraged data is monitored.

The sensitivity correction arithmetic operation unit 7 defines a pulsewave height value ΔI of a certain base line as a reference value, andstores a relationship between a result (second sensitivity correctionvalue k2) obtained by dividing the pulse wave height value ΔI by thereference value and the base line. The sensitivity correction arithmeticoperation unit 7 may store a relationship between a fluctuation in acurrent flowing to the TES 1, a fluctuation in pulse wave height valueΔI, and radiation energy for the purpose of further increasing accuracy.The second sensitivity correction value k2 changes to an increasingtrend in association with an increase in base line. When characteristicsof the second sensitivity correction value k2 and the base line are onceobtained, it is possible to obtain an accurate pulse wave height valueΔI by correcting a pulse wave height value ΔI which is actuallyobtained, using the second sensitivity correction value k2 correspondingto the actual base line. Hereinafter, a description will be given of anoperation example of the radiation analyzing apparatus 100 when thesensitivity correction arithmetic operation unit 7 acquires a firstsensitivity correction value k1 and a second sensitivity correctionvalue k2.

The sensitivity correction arithmetic operation unit 7 acquires a firstsensitivity correction value k1 and a second sensitivity correctionvalue k2 in an on-line mode during the execution of radiationmeasurement on an appropriate sample to be measured or in an off-linemode such as before the execution of radiation measurement on anappropriate sample to be measured or during the stopping of executionthereof. The sensitivity correction arithmetic operation unit 7 acquiresthe first sensitivity correction value k1 and the second sensitivitycorrection value k2 in accordance with operation conditions which areset in advance through the setting screen of the spectrum displaysection 8. As illustrated in FIG. 5, on the setting screen, a screen forsetting, for example, energy to be corrected, a target region (ROI) inthe vicinity of the energy to be corrected, the number of pieces ofsample data (number of counts), the order of a correction curve, and thelike is displayed. In addition, operation buttons for giving aninstruction for the execution of creating or recreating of a correctioncurve at an appropriate timing may be displayed on the setting screen.

The wave height analyzer 5 generates pre-sensitivity correction data PI0using signals sequentially transmitted from the room temperatureamplifier 15, a heater value HP (that is, a detection value of an outputof the heater) which is acquired from the temperature control section21, and a base line BL of a current flowing to the TES 1 which isacquired from the base line monitor mechanism 31. As illustrated in FIG.6, the pre-sensitivity correction data PI0 includes pieces of data of apulse wave height value PHA (=ΔI), a time t, a heater value HP, a baseline BL, a beam position bp, and a detector number dn. The wave heightanalyzer 5 outputs the pre-sensitivity correction data PI0 to thesensitivity correction arithmetic operation unit 7 to thereby receivepost-sensitivity correction data PI1 having been subjected tosensitivity correction from the sensitivity correction arithmeticoperation unit 7. The wave height analyzer 5 generates composite data(PI0, PI1) of a combination of the pre-sensitivity correction data PI0and the post-sensitivity correction data PI1, and outputs the compositedata (PI0, PI1) to the spectrum display section 8. That is, the waveheight analyzer 5 generates energy spectrum with respect to each ofpre-correction wave height value, which is based on a radiation pulsesignal output from the TES 1, and post-correction wave height value,which is obtained by performing sensitivity correction on thepre-correction wave height value is performed by the sensitivitycorrection arithmetic operation unit 7.

The sensitivity correction arithmetic operation unit 7 acquires a firstsensitivity correction value k1 and a second sensitivity correctionvalue k2 in accordance with operation conditions which are set inadvance through the setting screen of the spectrum display section 8,using pieces of pre-sensitivity correction data PI0 which aresequentially output from the wave height analyzer 5. The sensitivitycorrection arithmetic operation unit 7 acquires a plurality of pieces ofdata PI0 in a target region (ROI) in the vicinity of energy to becorrected (for example, 1487 eV which is an A1-Kα line) which is setthrough the setting screen. The sensitivity correction arithmeticoperation unit 7 calculates an average value of heater values HP and anaverage value of base lines BL from data PI0 for each number of piecesof sample data (for example, 1000 counts) which is set through thesetting screen. As illustrated in FIG. 7, the sensitivity correctionarithmetic operation unit 7 sets a center E0 of a spectrum formed bypieces of data PI0 for each number of counts which are set through thesetting screen, as a signal pulse output (that is, a pulse wave heightvalue PHA) corresponding to a combination of the calculated averagevalues of the heater values HP and the base lines BL. A method ofreading out the center of the spectrum includes, for example, thereading-out of the center of the spectrum through Gaussian fitting.

In this manner, the sensitivity correction arithmetic operation unit 7acquires corresponding data between a signal pulse output and acombination of the average values of the heater values HP and the baselines BL, for each number of counts which is set through the settingscreen. The sensitivity correction arithmetic operation unit 7 increasesthe number of pieces of corresponding data while storing pieces ofcorresponding data which are obtained as necessary, in order to increasethe accuracy of correction.

Incidentally, the sensitivity correction arithmetic operation unit 7 mayoutput a spectrum formed by pieces of data PI0 for each number of countswhich is set through the setting screen, and data such as the center E0of the spectrum read out through Gaussian fitting or the like to thespectrum display section 8 for the purpose of display.

The sensitivity correction arithmetic operation unit 7 calculates afirst sensitivity correction value k1 and a second sensitivitycorrection value k2 for a reference signal pulse output which is set inadvance, with respect to each of pieces of corresponding data which areobtained as necessary. The sensitivity correction arithmetic operationunit 7 sets a value obtained by dividing the reference signal pulseoutput by a signal pulse output corresponding to an average value ofheater values HP different from the reference heater value HP to be afirst sensitivity correction value k1. The sensitivity correctionarithmetic operation unit 7 sets a value obtained by dividing thereference signal pulse output by a signal pulse output corresponding toan average value of base lines BL different from the reference base lineBL to be a second sensitivity correction value k2. For example, in acase where a signal pulse output when the reference heater value HP is1.57 μW is set to 100.000 mV (equivalent to energy of 1487 eV to becorrected) and in a case where a signal pulse output when an averagevalue of heater values HP is 1.7258 μW is 101.015 mV, a value obtainedby dividing the reference signal pulse output by the signal pulse output(=100/101.015=0.989953) is set to be a first sensitivity correctionvalue k1.

As illustrated in FIGS. 8 and 9, the sensitivity correction arithmeticoperation unit 7 plots, in a graph, each of pieces of data ofcombinations of a first sensitivity correction value k1 and an averagevalue of heater values HP which are obtained as necessary and pieces ofdata of combinations of a second sensitivity correction value k2 and anaverage value of base lines BL while storing the pieces of data. Thesensitivity correction arithmetic operation unit 7 creates a correctioncurve using an n-order function (n is an integer) whose order is n,which is set through the setting screen, or a spline curve, with respectto a plurality of pieces of data which are updated while being stored asnecessary.

Incidentally, the sensitivity correction arithmetic operation unit 7 mayoutput pieces of data such as data of a combination of a firstsensitivity correction value k1 and an average value of heater valuesHP, data of a combination of a second sensitivity correction value k2and an average value of base lines BL, and the created correction curveto the spectrum display section 8 for the purpose of display for everyupdating.

Hereinafter, a description will be given of an operation example of theradiation analyzing apparatus 100 when the sensitivity correctionarithmetic operation unit 7 performs sensitivity correction using afirst sensitivity correction value k1 and a second sensitivitycorrection value k2 in an on-line mode or an off-line mode.

The sensitivity correction arithmetic operation unit 7 acquires a firstsensitivity correction value k1 and a second sensitivity correctionvalue k2 for heater values HP and base lines BL included inpre-sensitivity correction data PI0, from data of first sensitivitycorrection values k1 and second sensitivity correction values k2 whichare stored at each point in time, using the pieces of pre-sensitivitycorrection data PI0 which are sequentially output from the wave heightanalyzer 5 by radiation measurement for an appropriate sample to bemeasured, in an on-line mode. The sensitivity correction arithmeticoperation unit 7 corrects a pulse wave height value PHA to a pulse waveheight value PHA included in pre-sensitivity correction data PI0 byusing the first sensitivity correction value k1 and the secondsensitivity correction value k2. The sensitivity correction arithmeticoperation unit 7 generates post-sensitivity correction data PI1including the corrected pulse wave height value PHA and outputs thepost-sensitivity correction data PI1 to the wave height analyzer 5.Incidentally, the pre-sensitivity correction data PI0 and thepost-sensitivity correction data PH differ from each other in a pulsewave height value PHA according to the presence or absence ofsensitivity correction.

In addition, the sensitivity correction arithmetic operation unit 7corrects a pulse wave height value PHA included in each pre-sensitivitycorrection data PI0 using data of a first sensitivity correction valuek1 and a second sensitivity correction value k2 which are stored at eachpoint in time whenever a plurality of pieces of pre-sensitivitycorrection data PI0 stored in the wave height analyzer 5, spectrumdisplay section 8, or the like are sequentially acquired, in an off-linemode.

The spectrum display section 8 receives composite data (PI0, PI1)sequentially created by the wave height analyzer 5 to thereby display atleast one or both of a spectrum before sensitivity correction and aspectrum after sensitivity correction on a display in response to anoperator's request or the like. In addition, as illustrated in FIG. 7,the spectrum display section 8 displays a spectrum formed by pieces ofdata PI0 for each number of counts which are sequentially output by thesensitivity correction arithmetic operation unit 7, and data such as thecenter E0 of the spectrum on a display in response to an operator'srequest or the like. In addition, as illustrated in FIGS. 8 and 9, thespectrum display section 8 displays pieces of data such as data of acombination of each of first sensitivity correction values k1sequentially output by the sensitivity correction arithmetic operationunit 7 and an average value of heater values HP, data of a combinationof each of second sensitivity correction value k2 and an average valueof base lines BL, and a created correction curve on a display inresponse to an operator's request or the like.

As described above, according to the radiation analyzing apparatus 100of the present embodiment, there is provided the wave height analyzer 5that generates composite data (PI0, PI1) of a combination ofpre-sensitivity correction data PI0 and post-sensitivity correction dataPH in each of an on-line mode and an off-line mode, and thus it ispossible to perform various processes corresponding to each of thepresence and absence of sensitivity correction, and various types ofprocesses such as comparison between the presence and absence ofsensitivity correction.

Further, there is provided the sensitivity correction arithmeticoperation unit 7 that acquires a first sensitivity correction value k1and a second sensitivity correction value k2 using pieces ofpre-sensitivity correction data PI0 sequentially output from the waveheight analyzer 5 and corrects a pulse wave height value PHA included inthe data PI0, and thus it is possible to improve the correction accuracyof data while improving the accuracy of the first sensitivity correctionvalue k1 and the second sensitivity correction value k2 in associationwith the storage of data.

Further, the sensitivity correction arithmetic operation unit 7 acquiresa first sensitivity correction value k1 and a second sensitivitycorrection value k2 by pieces of data PI0 for each number of countswhich is set in advance, and thus it is possible to improve the accuracyof the first sensitivity correction value k1 and the second sensitivitycorrection value k2. Further, the first sensitivity correction value k1and the second sensitivity correction value k2 are repeatedly updated,and thus it is possible to improve the correction accuracy of data whileimproving the accuracy of the first sensitivity correction value k1 andthe second sensitivity correction value k2 in association with thestorage of data.

Further, there is provided the spectrum display section 8 that displaysat least one or both of a spectrum before sensitivity correction and aspectrum after sensitivity correction in response to an operator'srequest or the like using composite data (PI0, PI1), and thus it ispossible to improve user convenience.

Further, the spectrum display section 8 displays pieces of data such asdata of a combination of a first sensitivity correction value k1 and anaverage value of heater values HP, data of a combination of a secondsensitivity correction value k2 and an average value of base lines BL,and a created correction curve in response to an operator's request orthe like, and thus it is possible to easily visually ascertain theaccuracy of sensitivity correction performed by the sensitivitycorrection arithmetic operation unit 7.

Further, the spectrum display section 8 displays a setting screen forsetting operation conditions of the sensitivity correction performed bythe sensitivity correction arithmetic operation unit 7, and the like inresponse to an operator's input operation, and thus the operator caneasily control the state of sensitivity correction performed by thesensitivity correction arithmetic operation unit 7 in an on-line modeand an off-line mode.

Hereinafter, a modification example will be described.

In the above-described embodiment, the number of pieces of sample data(number of counts) is set through a setting screen of the spectrumdisplay section 8. However, the present invention is not limitedthereto, and a time may be set instead of the number of pieces of sampledata (number of counts).

In the above-described embodiment, the sensitivity correction of asignal pulse output is performed using a heater value HP and a base lineBL, but the present invention is not limited thereto.

The sensitivity correction arithmetic operation unit 7 may perform thesensitivity correction of a pulse wave height value PHA using at leastone of a heater value HP and a base line BL.

Incidentally, the technical scope of the present invention is notlimited to the above-described illustrative embodiment, and includesvarious modifications added to the above-describe illustrativeembodiment, without departing from the scope of the present invention.That is, the configuration of the above-described illustrativeembodiment is just an example, and a modification can be appropriatelymade.

What is claimed is:
 1. A radiation analyzing apparatus comprising: asuperconductive transition edge sensor configured to detect radiationand output a detection signal in accordance with sensitivity of thesuperconductive transition edge sensor; a data acquisition unitconfigured to acquire a physical quantity of data having correlationwith the sensitivity of the superconductive transition edge sensor; asensitivity correction unit configured to correct the detection signaloutput from the superconductive transition edge sensor by usinginformation regarding the correlation between the physical quantity ofdata acquired by the data acquisition unit and the sensitivity of thesuperconductive transition edge sensor; and a spectrum generation unitconfigured to generate an energy spectrum of the radiation based on thedetection signal output from the superconductive transition edge sensorand a signal obtained by performing sensitivity correction on thedetection signal by the sensitivity correction unit, wherein thespectrum generation unit is configured to output signal data thatincludes the physical quantity of data and the detection signal outputfrom the superconductive transition edge sensor, and wherein thesensitivity correction unit is configured to, by using the signal dataoutput from the spectrum generation unit, while generating theinformation regarding correlation between the physical quantity of dataand the sensitivity of the superconductive transition edge sensor,correct the detection signal by using the information regardingcorrelation.
 2. The radiation analyzing apparatus according to claim 1,wherein the sensitivity correction unit is configured to, by using thesignal data obtained over the period of time, repeatedly update theinformation regarding correlation for each period of time until apredetermined condition is satisfied.
 3. The radiation analyzingapparatus according to claim 1, wherein the data acquisition unitacquires an output of a heater, which is configured to heat thesuperconductive transition edge sensor, as the physical quantity.
 4. Theradiation analyzing apparatus according to claim 1, wherein the dataacquisition unit acquires a current flowing to the superconductivetransition edge sensor as the physical quantity.
 5. The radiationanalyzing apparatus according to claim 1, further comprising: a displayconfigured to display an energy spectrum of the radiation correspondingto each of presence and absence of sensitivity correction performed bythe sensitivity correction unit.
 6. The radiation analyzing apparatusaccording to claim 5, wherein the display is configured to display theinformation regarding the correlation.
 7. The radiation analyzingapparatus according to claim 5, wherein the display is configured todisplay a setting screen for setting conditions for generating theinformation regarding correlation by the sensitivity correction unit, inresponse to receiving an operator's input.